How do you validate the APHA/Pt-Co/Hazen Color Measurement with HunterLab instruments?

FAQ: “Our client is essentially claiming their APHA method is "better" than the one we are using with our HunterLab instrument. I'm inclined to believe they are wrong, but belief doesn't go very far in this industry. You sent me some great APHA documentation, but there is one thing that I know would quickly put this argument to rest. Do you have access to the actual validation performed by HunterLab on this instrument to validate the APHA method for use? Thanks for all of your help.”

Regretfully the details of our APHA correlation are proprietary although HunterLab does follow the industry accepted ASTM D1209/D5386 methodology for APHA Color correlation.

There is an easy method to self-validate the implementation of APHA/Pt-CO/Hazen Color at all sites in a way that is meaningful to measuring the trace yellowness of their product with their HunterLab instrument.

After standardization on the 10 mm cell filled with distilled water:

Read back the cell + water as a PQ Performance Qualification step. It should read water closely.

As an optional second PQ step, purchase a certified 3rd party APHA standard, typically just above your product range, and read it. It should read closely to the assigned value.

As an optional third PQ step, purchase a certified 3rd party APHA standard in the middle of your product range, and read it. It should read closely as assigned.

These PQ APHA Color standards can be used to self-certify the APHA Color performance of your instrument over time. The results can be entered in an SPC (Statistical Process Control) chart along with the APHA product color values of multiple lots.